如何遍历 motoko 中的内部数组？

Question

我是 motoko 和互联网计算机的新手，当我工作时，我遇到了太多看似简单的困难，我很难做到这一点，在此处发布 link 到论坛问题

https://forum.dfinity.org/t/how-to-traverse-inner-array-of-a-trie/12941?u=manubodhi

如果有人精通 motoko 和 difinity，请帮忙

Answer 1

我在motoko playground 中为您准备了一个小代码，以了解您如何遍历内部数组并实现过滤Trie 的目标。这是在 motoko playground 中保存的项目：https://m7sm4-2iaaa-aaaab-qabra-cai.raw.ic0.app/?tag=1150943578

很快要通过内部数组进行过滤，您可以使用：

let trieOfDishes = Trie.filter<DishId, Dish>(dishes, func (k, v) {
    Array.find<MealTypeId>(v.mealTypeId, func(x : MealTypeId) { x == mealTypeId }) != null ;
});

容器实现的完整代码：

import Trie "mo:base/Trie";
import Array "mo:base/Array";
import Iter "mo:base/Iter";
import Nat32 "mo:base/Nat32";

actor Dishes {
    
    type DishId = Nat32;
    type DishTypeId = Nat32;
    type MealTypeId = Nat32;

    public type Dish = {
        dishId: DishId;
        dishTypeId : DishTypeId;
        mealTypeId : [MealTypeId]
    };

    var dishes: Trie.Trie<DishId, Dish> = Trie.empty();

    private func key(x : DishId) : Trie.Key<DishId> {
        return { hash = x; key = x };
    };
    
    public func add_dish(dish: Dish) : async Dish {
        dishes := Trie.replace(dishes, key(dish.dishId), Nat32.equal, ?dish).0;
        return dish;
    };

    public query func getDishesByDishId (dishTypeId : DishTypeId) : async [(DishId, Dish)] {
       let trieOfDishes = Trie.filter<DishId, Dish>(dishes, func (k, v) { v.dishId == dishTypeId } );
       let arrayOfDishes : [(DishId, Dish)] = Iter.toArray(Trie.iter(trieOfDishes));
       return arrayOfDishes;
    };

    public query func getDishesBymealTypeId (mealTypeId : MealTypeId) : async [(DishId, Dish)] {
       let trieOfDishes = Trie.filter<DishId, Dish>(dishes, func (k, v) {
            Array.find<MealTypeId>(v.mealTypeId, func(x : MealTypeId) { x == mealTypeId }) != null ;
       });
       let arrayOfDishes : [(DishId, Dish)] = Iter.toArray(Trie.iter(trieOfDishes));
       return arrayOfDishes;
    };
    
}

如何遍历 motoko 中的内部数组？

How to traverse an inner array in motoko?

dfinity

motoko

internet-computer